The present disclosure relates to fuel tank vent valves, and particularly to venting apparatus which operates to seal the vapor space in the interior of a fuel tank at the completion of vehicle refueling and reopens at some point after refueling has been completed to vent the vapor space. More particularly, the present disclosure relates to a fill-limit valve system for controlling tank ventilation and for preventing overfilling of a vehicle fuel tank and for controlling flow of fuel vapor and liquid fuel through an aperture in a fuel tank.
Fuel-dispensing pump nozzles are known to include a fill-limiting sensor for shutting off the flow of fuel from the nozzle when a vehicle fuel tank is nearly filled. Typically, this fill-limiting sensor is triggered whenever the fuel tank is full and fuel “backs up” the tank filler neck to splash onto or reach the fill-limiting sensor located on the nozzle. Sometimes fuel pump operators overfill a fuel tank inadvertently in a good-faith effort to fill the tank “completely” or to purchase a quantity of fuel that can be paid for in cash without causing the operator to receive unwanted coinage in change.
During cornering, the liquid fuel inside a vehicle fuel tank is often agitated to cause the liquid fuel to move with a splashing motion inside the vehicle fuel tank. Liquid fuel can also be sloshed about in a vehicle fuel tank in response to other types of vehicle motion in addition to vehicle cornering.
Vehicle fuel tanks include vent apparatus for regulating discharge of liquid fuel and fuel vapor from the interior region of the fuel tank. Such a vent apparatus is often mounted in an aperture formed in a top wall of the vehicle fuel tank and could be exposed to rising levels of liquid fuel in the fuel tank during refueling and/or to agitated liquid fuel that is sloshed about inside the vehicle fuel tank during cornering or other movement of the vehicle. This type of vent apparatus often includes a buoyant “float valve” that is movable in a fuel tank to open and close a fuel tank venting outlet and that is capable of floating in liquid fuel once the liquid fuel rises to a certain level in the fuel tank. During tank refueling and sometimes during fuel sloshing, float valves are moved by liquid fuel to close tank venting outlets.